MTBF / MTTR / Availability
Enter the data of a machine or a line over a period (a month, a shift, whatever you have recorded) and calculate the three indicators instantly.
MTBF
125.0 h
MTTR
2.0 h
Availability
98.4%
The equipment fails rarely but each repair weighs relatively more: the problem is RELIABILITY. It is better to attack the failure frequency (RCM, predictive) before the repair speed.
How it works
You enter the operating hours of the period, the number of failures and the total repair hours. With that it calculates:
- MTBF (mean time between failures) = operating hours ÷ number of failures.
- MTTR (mean time to repair) = repair hours ÷ number of failures.
- Availability = MTBF ÷ (MTBF + MTTR): the fraction of time the equipment is in condition to work.
If there were no failures, availability is 100% and there is no MTBF or MTTR to calculate. The diagnosis compares MTBF with MTTR: with a ratio of 20 or more, reliability dominates (it fails rarely and is repaired quickly); with 5 or less, maintainability dominates (what weighs is how long the repair takes); between 5 and 20, it is mixed. Those two cut-offs are a rule of thumb of this site, they do not come from any source.
Beware of few failures: with two or three events the MTBF changes a lot from one period to another, so it is best to look at several periods before drawing conclusions.
Sources
These are the ones from the article where the theory behind this tool is developed.
Formulas, examples and why a high MTBF can be misleading? It is all explained in the article MTBF, MTTR and Availability: how to calculate them.